This invention relates to automatically actuated valves, and more particularly, to a system which is capable of automatically regulating the flow of natural gas in pipelines.
Natural gas flows from municipal gas mains to customer locations. At a customer location, gas is routed through smaller pipes into a gas meter. Pipes then carry the gas into a customer residence or business where the gas is ultimately used by appliances or other gas-consuming devices. While gas mains are susceptible to rupture from the violent vibrations caused by earthquakes, the smaller pipes leading into a residence or business are often at higher risk of rupture. In the aftermath of an earthquake, the damage resulting from fires caused by gas pipe rupture can oftentimes exceed the damage resulting from shaking caused by the earthquake.
There are numerous prior art proposals for gas shut-off valves which are designed to respond to earthquakes. Such proposals typically cause false shut-offs in response to non-earthquake vibrations. Furthermore, the prior art shut-off systems proceed to shut-off the gas flow regardless of whether there is a rupture in the gas line. This can result in repeated loss of gas service. As a result, these prior art systems are rarely implemented on a wide scale.
Thus there is the need for a relatively simple, cost-effective system, which can reliably detect the rupture of natural gas pipelines due to earthquake vibration and, in turn, shut-off gas supply only when warranted.
In accordance with one embodiment of the invention, an automatically actuated regulation system for a natural gas pipeline comprises a flow control device, a vibration sensor, a gas flow meter, a trigger unit, and a microprocessor. The microprocessor prompts the flow control device to restrict the flow of gas when two conditions are preferably met. The first condition is met when the vibration sensor detects a vibration that surpasses a predetermined threshold value. The second condition is met when the flow rate in the natural gas pipeline has increased over the flow rate before the vibration. The microprocessor receives data from the vibration sensor and the flow meter. Comparisons are then made and the flow control unit is actuated when the conditions are met.
In another embodiment of the invention, an automatically actuated regulation system for gas and other fluids flowing in a pipeline incorporates a mechanical gas flow meter that provides a mechanical output signal corresponding to the measure of gas flow through the pipeline. Preferably, this is a diaphragm type meter provided by the utility company. The meter is coupled to a means for converting the mechanical output signal to an electrical output signal. In turn, the conversion means is coupled to a microprocessor that is configured to control the regulation system. As with the above embodiment, the system includes a flow control device, a vibration sensor, and a trigger unit. The microprocessor prompts the flow control device to restrict the flow of gas when two conditions are preferably met as described above.
In yet another embodiment of the invention, the system also comprises a modem that is capable of transmitting and receiving data over a communication line. Thus, data from the regulation system can be examined at locations other than the place where the system is situated.